\name{print.data.table}
\alias{print.data.table}
\title{ data.table Printing Options }
\description{
  \code{print.data.table} extends the functionalities of \code{print.data.frame}.

  Key enhancements include automatic output compression of many observations and concise column-wise \code{class} summary.
}
\usage{
  \method{print}{data.table}(x,
    topn=getOption("datatable.print.topn"),          # default: 5
    nrows=getOption("datatable.print.nrows"),        # default: 100
    class=getOption("datatable.print.class"),  # default: FALSE
    row.names=getOption("datatable.print.rownames"), # default: TRUE
    col.names=getOption("datatable.print.colnames"), # default: "auto"
    print.keys=getOption("datatable.print.keys"),    # default: FALSE
    quote=FALSE,
    timezone=FALSE, \dots)
}
\arguments{
  \item{x}{ A \code{data.table}. }
  \item{topn}{ The number of rows to be printed from the beginning and end of tables with more than \code{nrows} rows. }
  \item{nrows}{ The number of rows which will be printed before truncation is enforced. }
  \item{class}{ If \code{TRUE}, the resulting output will include above each column its storage class (or a self-evident abbreviation thereof). }
  \item{row.names}{ If \code{TRUE}, row indices will be printed alongside \code{x}. }
  \item{col.names}{ One of three flavours for controlling the display of column names in output. \code{"auto"} includes column names above the data, as well as below the table if \code{nrow(x) > 20}. \code{"top"} excludes this lower register when applicable, and \code{"none"} suppresses column names altogether (as well as column classes if \code{class = TRUE}. }
  \item{print.keys}{ If \code{TRUE}, any \code{\link{key}} and/or \code{\link[=indices]{index}} currently assigned to \code{x} will be printed prior to the preview of the data. }
  \item{quote}{ If \code{TRUE}, all output will appear in quotes, as in \code{print.default}. }
  \item{timezone}{ If \code{TRUE}, time columns of class POSIXct or POSIXlt will be printed with their timezones (if attribute is available). }
  \item{\dots}{ Other arguments ultimately passed to \code{format}. }
}
\details{
  By default, with an eye to the typically large number of observations in a code{data.table}, only the beginning and end of the object are displayed (specifically, \code{head(x, topn)} and \code{tail(x, topn)} are displayed unless \code{nrow(x) < nrows}, in which case all rows will print).
}
\seealso{\code{\link{print.default}}}
\examples{
  #output compression
  DT <- data.table(a = 1:1000)
  print(DT, nrows = 100, topn = 4)

  #`quote` can be used to identify whitespace
  DT <- data.table(blanks = c(" 12", " 34"),
                   noblanks = c("12", "34"))
  print(DT, quote = TRUE)

  #`class` provides handy column type summaries at a glance
  DT <- data.table(a = vector("integer", 3),
                   b = vector("complex", 3),
                   c = as.IDate(paste0("2016-02-0", 1:3)))
  print(DT, class = TRUE)

  #`row.names` can be eliminated to save space
  DT <- data.table(a = 1:3)
  print(DT, row.names = FALSE)

  #`print.keys` can alert which columns are currently keys
  DT <- data.table(a=1:3, b=4:6, c=7:9, key="b,a")
  setindexv(DT, c("a", "b"))
  setindexv(DT, "a")
  print(DT, print.keys=TRUE)
}

